JPS5897608A - Method and device for surface property - Google Patents

Abstract

PURPOSE:To quantify the surface properties of a body to be measured accurately and easily by Fourier-transforming a spatial light intensity distribution in the surface of the body to be measured and measuring light power intensity of specific space frequency. CONSTITUTION:A rectangular pattern is reflected by the surface of a body to be measured and projected and imaged on the image formation surface of a linear solid-state image sensor 20. A spatial light intensity distribution signal obtained through the photoelectric conversion of the image sensor 20 is sent to a monitoring device 21 for a spatial light intensity distribution through a control circuit 22 and also sent to a microcomputer 24 through an interface 23. The microcomputer 24 processes the spatial light intensity distribution by Fourier transform to quantify the definition, luster, or surface roughness of the surface of said body according to the light power intensity of specific space frequency. The result is outputted to a printer 25, graphic display 26, graphic hard copying device 27, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Methods and apparatus for measuring sharpness, gloss, and surface roughness (related thereto).

Gloss and surface roughness are important factors that determine the properties of an object's surface, and are as important characteristics as color, especially in evaluating the finished state of a paint film. For gloss measurement method, please refer to JI
S, Z-8741 specifies specular gloss and contrast gloss as physical gloss, and definition gloss as psychological gloss. quantification is the slowest, and even today, this evaluation is still based on visual sensory evaluation of living organisms. According to JIS, the definition of sharpness gloss is ``the extent to which the image of another object is transferred to the back surface.'' Based on this definition, some sharpness gloss meters have been devised. One of them is disclosed in Utility Model Publication No. 41-19039 (which quantifies the extent to which images of character patterns of various sizes projected on the surface of an object to be measured can be read). , it is not used much because the measured values vary due to individual differences between the measurers and the resolution of the measured values is poor.

Furthermore, in the example disclosed in JP-A No. 50-153979, a pattern having bright and dark boundaries is imaged through reflection on the surface of the object to be measured, and the received light intensity changes at the bright and dark boundary portions in the imaged pattern. This method quantifies the sharpness and glossiness based on the ratio, but in this method, the measured value is directly affected by fluctuations in the received light intensity due to changes in the reflectance of the surface to be measured, and also due to the unevenness of the surface to be measured. Due to these properties, the received light intensity distribution does not monotonically decrease, and there are problems such as difficulty in signal processing for quantifying sharpness and gloss from the rate of change in received light intensity.

Furthermore, as another example, for example, JP-A-52-1389
The characteristics of the sharpness gloss meter I Kotsushi disclosed in No. 60 will be explained with reference to FIG. Figure $1 (The optical system shown here consists of a light source 1, slit 2, and lens 3. Parallel light rays are incident on the surface 4 of the object to be measured in a direction of 45 degrees or 60 degrees.The reflected light C reflects the state of the surface of the object to be measured. It will be scattered according to the

Sharpness gloss is an optical measurement of how clear the reflected light of the slit image is on the iQ-N6.The maximum value of the transmitted light in the bright part of the A turn is M, and the minimum value in the dark part is m.
is defined by the following equation.

The larger C is, the higher the sharpness is, and the smaller C is, the lower the sharpness is. However, a problem with this device is that the measured values change due to the influence of ambient light, and that the projected pattern image shifts from the position of the light receiving aperture of the light receiver 7 due to warpage or curvature of the surface of the object to be measured. It has drawbacks such as change or unmeasurability.

Therefore, the present invention is capable of evaluating the surface properties, such as sharpness and gloss, based on how sharply the edges of the rectangular wave pattern are reflected on the surface of the object to be measured. There is a strong positive correlation between the sharpness of the light intensity distribution on the imaging plane and the sharpness of the edges of the rectangular wave nocturne imaged on the surface of the object to be measured. This method was developed based on the fact that spatial frequency analysis of the light intensity distribution would result in stronger high-frequency components. The spatial light intensity distribution on the image forming surface is Fourier-transformed, and the sharpness, gloss, or surface roughness of the surface of the object to be measured is determined by the magnitude of the light intensity at a specific spatial frequency. By quantifying, it is possible not only to eliminate the influence of individual differences among the measurers and improve resolution, but also to eliminate the influence of warpage and curl of the measured surface value on the measured value, which were the drawbacks of existing measurement methods. The objective is to provide a new surface texture measurement method that can accurately and easily quantify the surface texture by minimizing the influence of differences in the reflectance of the surface to be measured on measured values, as well as the influence of changes in the level of ambient light. It is said that

The present invention also provides an illumination optical system that illuminates a slit from behind, an imaging optical system that projects an image of the slit onto an imaging plane through reflection on the surface of a measured object, and a a photoelectric element that converts a spatial light intensity distribution into an electrical signal; a Fourier transform of the spatial light intensity distribution signal from the photoelectric element;
It is configured with a data processing system that calculates the optical power intensity at a specific spatial frequency, and it is possible to calculate the surface The purpose of this invention is to provide a new device that can accurately and easily quantify properties.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 2 shows an example of the configuration of the optical system of this device. Optical rails 12 and 13 and a fine movement stage 14 are arranged on the optical bench 10 so as to be rotatable about the rotation axis connector 11, and the optical rails 12 are arranged in such a way that the length direction of the slit is parallel to the paper surface. A slit 16 whose diameter can be varied in the range of 0.1 to 2 digits, and a light source 15 for illuminating the slit 16 are arranged, and a projection imaging lens 19 and a -dimensional solid-state image sensor 20 are arranged on the optical rail 13. (For example, 2
A Fort diode array consisting of 512 photodiodes arranged in a row is arranged in a direction such that the light receiving parts are arranged perpendicular to the plane of the paper.

The optical rails 12 and 13 are equipped with a length measurement scale, and a light source 15 is arranged on the optical rails 12 and 13 in a forward and backward direction.
The structure is such that the positions of the slit 1'6, the projection imaging lens 19, and the -dimensional solid-state image sensor 20 can be read.

Further, the optical rails 12 and 13 are connected to the rotating shaft connector 11, and the angle between the moving direction of the fine movement stage 14 shown by the arrow ■ and the optical rail 12, and the angle between the fine movement stage 1
The angles formed between the moving direction of 4 and the optical rail 13 are each 20
There is a T k fi tank structure that can be set in the range of ~80 degrees, and the set angle can be read by the angle scale graduated on the rotary shaft connector. A sample holder 17 is attached to the fine movement stage 14 , and the object to be measured 18 can be attached to the sample holder 17 so that its surface direction is substantially perpendicular to the moving direction of the fine movement stage 14 .

The spatial light intensity distribution in the slit 16 can be considered to be an ideal rectangular wave, and this ideal rectangular wave pattern is projected onto the imaging lens 1 through reflection on the surface of the object to be measured 18.
When a projection image is formed by 9, it is diffused or scattered depending on the surface condition of the object to be measured 18, and the ideal rectangular waveform becomes distorted. is shown in Figure 3. The horizontal axis in FIG. 3 indicates the spatial distance in the direction perpendicular to the plane of the drawing of the projection image plane where the one-dimensional solid-state image sensor 20 is arranged, and the vertical axis indicates the light intensity.

As a method for quantifying this projection imaging pattern, we apply the theory of Fourier series expansion, which states that patterns in which the boundary between bright and dark areas of a projection imaging pattern changes sharply have a strong spatial high frequency component intensity. With the aim of achieving this, the spatial light intensity distribution is Fourier transformed, a power spectrum normalized by the DC component intensity is calculated, and the power intensity at a specific frequency of the power spectrum is used as the sharpness gloss value. FIG. 4 shows an example of power spectrum data calculated from the example of spatial light intensity distribution data shown in FIG. The horizontal axis in Fig. 4 shows the spatial frequency, and the vertical axis shows the power intensity with the DC component intensity as 1.The data of A, B, and C shown in Fig. 4 are shown in Fig. 3. A, B,
It corresponds to the data of C. Thereby, as shown in FIG. 4, the sharpness and gloss can be quantified based on the magnitude of the optical power intensity at an appropriate number of spatial rotations @, , fx.

In addition, Figures 5, 6, and 7 show the imaging pattern or the case of a single slit, and the distance in the slit is 0.1 m + 0.2 m, respectively.

0.4, the imaging magnification is 1.8 times, and the projection angle and reception angle with respect to the surface of the object to be measured are 45 degrees. Based on this data example, the spatial frequency at which sharpness and gloss can be easily detected is determined by using a slit width that is twice the width of the slit image to be formed on the imaging surface on an ideal mirror surface, and a projection angle. In the data example where the acceptance angle is 70 degrees and the imaging magnification is 1.3 times, the frequencies with good detectability are as follows.Each curve in Figures 9 to 9 above represents the surface texture of each object to be measured. represent.

Furthermore, the method of the present invention, which measures sharpness and gloss using a power spectrum, has many features as described below, and is a practically advantageous method. That is, in FIG. 3, the position of the projected image formation pattern is -dimensional solid-state image sensor 2
0 measurement window, the power spectrum is in principle the same regardless of its position, and even if the received light intensity changes, the power spectrum is in principle the same. This minimizes the effects of changes in the reflecting device due to differences in the reflectance of the surface of the object to be measured, and shifts in the position of the projected image pattern due to warping or curling of the surface of the object to be measured, and allows only the shape of the projected image pattern to be reflected. It has the feature of extracting information, and these features are advantageous when specifically configuring the sharpness/gloss measuring device according to the method of the present invention.

In addition, in the above practical example, the light intensity distribution of a single slit was Fourier-expanded to find the power intensity for a specific spatial frequency, but the light intensity distribution for multiple slits was Fourier-expanded to find the power intensity for a specific spatial frequency. The gloss sharpness may be measured using this repeated data.

Next, detect the spatial light intensity distribution of the projection imaging pattern,
A data processing system for performing arithmetic processing will be described in detail with reference to a block diagram of an embodiment shown in FIG. The spatial light intensity distribution signal photoelectrically converted by the -dimensional solid-state image sensor 20 is the -dimensional solid-state image sensor 2
The signal is sent to the spatial light intensity distribution monitoring device 21 via the control circuit 22 which has the functions of driving the signal, reading out the signal, and amplifying the signal. Sent to 23. Based on the command signal from the microcomputer 24,
At the interface 23, the spatial light intensity distribution signal, which is a pulsed signal, is sampled and held, and further converted into an analog-to-digital signal.
stored in the internal buffer memory. Next, the microcomputer 24 reads out the spatial light intensity distribution data stored in the buffer memory in the interface 23,
Necessary processing such as power spectrum calculation can be performed, and the results can be output to a printer 25, a graphic display device 26, a graphic hard copy device 27, etc., as necessary.

When calculating the sharpness gloss value by the microcomputer 24, it is not necessary to calculate the power spectrum over the entire spatial frequency range, but depending on the range of sharpness gloss to be measured, it is necessary to calculate the power spectrum in a specific range or at a specific spatial frequency. Only the power intensity may be calculated.

In addition, the microcomputer 24 not only calculates the sharpness gloss value from the spatial light intensity distribution data obtained from the one-dimensional solid-state image sensor 20, but also can calculate the projection imaging magnification by a program, and display The position of the optical system can be adjusted depending on the magnification, and if necessary, the position adjustment can be automated. Furthermore, the microcomputer 24 can also detect the focal position according to a program, and depending on the displayed focal position information, the imaging optical system consisting of the projection imaging lens 19 and the one-dimensional solid-state image sensor 20 or the object to be measured 18 can be detected. It is possible to adjust the position of the attached sample holder 17, and if necessary, it is also possible to visualize the position adjustment.

FIG. 11 shows an example of correspondence data between the sharpness and gloss of the coating surface measured numerically based on the power intensity with respect to a specific spatial frequency using the apparatus of the present invention, and visual evaluation. ! 1
In FIG. 1, the horizontal axis shows the visual evaluation value, and the vertical axis shows the measured value by the apparatus of the present invention. This shows that the two are highly correlated.

Next, surface roughness measurement according to the present invention will be described. Since it is predicted that there is a close relationship between the gloss and surface roughness of the surface of an object, we investigated the relationship between the values measured by the sharpness gloss measuring device of the present invention and the surface roughness. FIG. 12 shows an example of measurement using a certain coating film as the object to be measured. In Fig. 12, the horizontal axis is the average roughness measured by the stylus roughness meter, and the vertical axis is the measured value by the device of the present invention, and A and B in the figure indicate the difference in the slit. It is clear from Fig. 12 that there is a certain relationship between the average roughness and the measured value, and that the device of the present invention can also be used as a surface roughness measuring device. The roughness of soft object surfaces, which cannot be measured with a meter, can also be measured without contact.

However, as suggested by the 1ilZ diagram, it is desirable to set the inside of the slit appropriately depending on the surface roughness area to be measured. That is, when the average roughness is large, the inside of the slit is set to be large as shown by curve B in FIG. 12, and when the average roughness is small, the inside of the slit is set to be small as shown by curve A in FIG. is desirable. Based on these findings, we conducted various experimental studies on the characteristics of the device of the present invention, and found that in both the measurement of sharpness, gloss, and surface roughness, the sharpness, gloss, and surface roughness of the surface of the object to be measured. Set the detection area of the sensor, and configure the appropriate optical system according to the detection area, i.e., the settings in the slit, the emission angle, the acceptance angle setting,
It has become clear that it is desirable to set the projection imaging magnification, and that it is practically sufficient to have the axial rotation described in Claims Nos. 31 to 41 and 51.

Furthermore, in view of the fact that non-contact measurement is possible, which is one of the features of the present invention, a device for further increasing the usefulness of the sharpness gloss measuring device and the surface roughness measuring device according to the present invention is shown in Fig. 13 below. This will be explained in detail based on the example shown below. In FIG. 13, a chamber 3 capable of housing a sample holder 17 with a measured object 18 attached thereto.
0 so that the object to be measured 18 and the sample holder 17 can be separated from the outside air. The chamber 30 has measurement windows 31 and 32 made of optical glass, and a door (not shown) for taking the object 18 in and out of the chamber 30.

The chamber 30 is connected to a constant temperature and humidity chamber 36 through a filter 33, a duct 34, and a blower 35.Although not clearly shown in FIG. The structure allows the air to flow in a direction perpendicular to the sample holder 17, so that the air flow is less likely to be obstructed by the sample holder 17. Further, a wind speed sensor 41, a wind temperature sensor 42, and a humidity sensor 43 are provided in the chamber 30 to detect wind speed, wind temperature, and humidity, and the output from each sensor is sent to a signal converter 44. After being converted into a predetermined electrical signal, the signal is sent to a recorder 45 for recording, and is also sent to a blower rotation speed control device 46 and a temperature/humidity control device 47.

Although the temperature and humidity control device 47 is not shown, it operates a heater, a cooler, and a humidifier to control the air in the thermostatic chamber 36 to a predetermined temperature and humidity state, while the blower rotation speed control device 46
The rotational speed of the blower 35 is controlled so that the air flow velocity within the chamber 30 becomes a predetermined flow velocity.

With the above configuration, it is possible to circulate air at a predetermined temperature and humidity within the chamber 30 at a predetermined flow rate. This device can be used to measure sharpness, gloss, and surface roughness when they are affected by environmental conditions and non-contact measurement is required. It is now possible to track temporal changes in clarity, gloss, or surface roughness due to surface drying, and is extremely useful for analyzing the drying behavior of paint films, which have a large impact on the finished surface properties of paint films, and for understanding the effects of painting work conditions. Valid and disputed.

As has become clear from the above description, the method and apparatus for measuring the surface properties of sharpness, gloss, and surface roughness according to the present invention is the most common method for human visual evaluation, and This method faithfully quantitatively evaluates "the degree to which the image of another object is transferred to the surface" as defined in JIS-Z-8741, and also evaluates the reflectance of the surface of the object to be measured, which is a drawback of conventional methods. It has the excellent feature of being able to extremely minimize the effects of warpage and curling of the surface of the object to be measured.It also has the excellent feature of minimizing the effects of warpage and curling of the surface of the object to be measured. It also has the advantage of being able to accurately and quickly adjust the projection imaging magnification and focus position by processing the information, and the overall effect of these functions is to provide excellent measurement results. It is possible to obtain repeatability accuracy.

Furthermore, by being able to vary the slit width, projection angle, reception angle, and projection imaging magnification, it is possible to measure a wide range of clarity, gloss, and surface roughness, and furthermore, the implementation of the present invention does not require expensive optical elements. It has many advantages, such as being able to be constructed using inexpensive optical elements.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of a known sharpness gloss measuring device, FIGS. 2 and 13 are diagrams showing an embodiment of the device of the present invention, and FIG. hail diagram,
Figure 4 shows the power spectrum of the spatial light intensity distribution in Figure 3, Figures 5.6°7, 8.9. The figures show the power spectra of other measurement examples, Figure 10 is a block diagram of a data processing device according to an embodiment of the present invention, and Figure 11 is a visual observation of the measured values and sharpness and gloss by the device of the present invention. FIG. 12 is a diagram showing the correspondence relationship between the evaluation values and the average roughness measured by the device of the present invention and the average roughness measured by the stylus roughness meter. 10...Optical bench, 12.13...Optical rail, 15
... Light source, 16... Slit, 18... Measured object, 20... One-dimensional fixed image sensor. Patent applicant: Nippon Paint Co., Ltd. Patent attorney Aoyama Aoyama and two people Figure 6 AI for Uzeki! ;L (〆昂 leave) Figure 7 0246810121416 old 202224267-'
t Tsuji space @ Anni (X 烏合:・ Fig. 8 '2' l [Mugi (X Book Rigo) Fig. 9 pi moat board (X 茧目-left)

Claims (7)

[Claims] (1) A rectangular wave pattern is projected and imaged onto an imaging plane by an imaging optical system through reflection on the surface of the object to be measured, and the spatial light intensity distribution on the imaging plane is Fourier-transformed into a specific space. A method for measuring surface properties, characterized in that the sharpness, gloss, or surface roughness of a surface of an object to be measured is quantified based on the magnitude of optical power intensity at different frequencies. (2) An illumination optical system that illuminates the slit from behind, an imaging optical system that projects and forms an image of the slit onto an imaging plane through reflection on the surface of the object to be measured, and a spatial Clarity, gloss, or A device that measures surface roughness. (3) The device according to claim 2, characterized in that it is equipped with a mechanism that can vary the width of the slit within a range of 0.1 to 2 rm. (4) In the apparatus according to claim 2 above, the slit image is projected and imaged with the optical axis of the illumination system that illuminates the slit and the optical system that includes the slit, substantially perpendicular to the surface of the object to be measured. In a plane that includes the optical axis of the imaging optical system, the projection angle between the perpendicular to the surface of the object to be measured and the optical axis of the optical system including the illumination system and the slit, and the angle between the normal to the surface of the object to be measured and the imaging optical system. A device characterized by comprising a mechanism that can vary the light receiving angle formed with the optical axis within a range of 20 to 80 degrees. (5) In the apparatus according to claim 2, the projection imaging magnification when projecting the slit image through reflection on the surface of the object to be measured can be varied in the range of 0.5 to 20 times. A device characterized by comprising a mechanism. (6) In the apparatus according to claim 2, the focus is detected based on the spatial light intensity distribution signal of the slit image on the imaging plane, and the eye movement detects the object to be measured or the imaging optical system and the photoelectron. An apparatus comprising a mechanism for moving a conversion element to a focused position. (7) The apparatus according to claim 2, characterized in that it is equipped with a mechanism that can control the temperature, humidity, and wind speed of the space in which the object to be measured is placed.